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A comparative study of the seed germination biology of a narrow endemic and two geographically-widespread species of Solidago (Asteraceae). 1. Germination phenology and effect of cold stratification on germination

Published online by Cambridge University Press:  19 September 2008

Jeffrey L. Walck
Affiliation:
School of Biological Sciences, University of Kentucky, Lexington, Kentucky 40506-0225, USA
Jerry M. Baskin
Affiliation:
School of Biological Sciences, University of Kentucky, Lexington, Kentucky 40506-0225, USA
Carol C. Baskin
Affiliation:
School of Biological Sciences, University of Kentucky, Lexington, Kentucky 40506-0225, USA

Abstract

Solidago shortii is endemic to a small area in northcentral Kentucky (USA), whereas two of its sympatric congeners, S. altissima and S. nemoralis, are geographically widespread. Seeds (achenes) of S. shortii (0.370 mg) are significantly larger (PLSD, P=0.05) than those of S. altissima (0.070 mg) and S. nemoralis (0.068 mg). Germination percentages of freshly-matured seeds of the three Solidago species collected in November 1991, 1992 and 1994 were 0–2% in light at 15/6°C, 1–37% at 20/10°C, 9–56% at 25/15°C and 10–85% at 30/15 and 35/20°C. Stratification increased the percentage and rate of germination and decreased the time to the onset of germination (measured by Timson's index only at 20/10°C in light) in the three species. Following 12 weeks of cold stratification in light, seeds of the three species germinated to 72–100% in the light and to 22–100% in darkness over the range of thermoperiods; those cold-stratified in darkness germinated to 39–100% in light. Freshly-matured seeds of S. altissima and of S. nemoralis germinated to 0–4% in darkness, whereas those cold-stratified for 12 weeks in darkness germinated to 0–28% in darkness. On the other hand, freshly-matured and cold-stratified (in darkness) seeds of S. shortii germinated to 0–13 and 13–73%, respectively, in darkness. Under near-natural temperatures in a glasshouse without temperature control, germination of the three species peaked in March. Thus, the primary difference in dormancy-breaking and germination requirements of the three species is that the endemic germinates to a much higher percentage in darkness than its two congeners. Seeds of S. shortii do not have any special dormancy-breaking or germination requirements that could not be fulfilled outside its present-day geographic range.

Information

Type
Ecophysiology
Copyright
Copyright © Cambridge University Press 1997

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